Brooklyn, 1942. War rages overseas as brother and sister Will and Maggie Scripps contribute to the war effort stateside. Ambitious Will secretly scouts for the Manhattan Project while grief-stricken Maggie works at the Navy Yard, writing letters to her dead mother between shifts.
But the siblings’ quiet lives change when they discover a beautiful woman hiding under their back stairs. This stranger harbors an obsession with poisons, an affection for fine things, and a singular talent for killing small creatures. As she draws Will and Maggie deeper into her mysterious past, they both begin to suspect she’s quite dangerous―all while falling helplessly under her spell.